This invention relates in general to communication systems and more particularly to a method and system for improving the integrity of a distributed power communication system for controlling the functionality of one or more mobile assets remote from a lead mobile asset.
Communication among locomotives and other cars in a train consist, for example, is important to ensure the coordination of various functions of the locomotives such as throttle control, braking and direction during the train""s operation. Radio frequency schemes may be used for such intra-train communication with various combinations of transmitters, receivers and/or transceivers being distributed among the lead or controlling locomotive and the remote locomotives under the control of the lead. During a locomotive distributed power communication operation the lead or command locomotive may transmit control information in a command message to one or more remote or controlled locomotives that are located further back in the train consist. On receipt of the command message, each remote locomotive may transmit a reply message back to the lead locomotive including operational status information of that remote. The operational status message verifies to the lead locomotive that the remote is operating in response to the command message instructions. If the lead locomotive is satisfied that it has received a reply message from all of the remote locomotives then the lead locomotive may declare that all remote locomotives are following the command message instructions. Alternatively, if the lead locomotive does not receive a reply message from each remote unit within a certain period of time then the lead locomotive may assume that communication has been lost and that one or more of the remote locomotives is not following the command message instructions. However, the lead locomotive not receiving a reply message from one or more remote locomotives does not necessarily mean that those locomotives are not following the command message instruction.
For example, locomotive train consists traverse a wide range of topographies including mountainous terrain and other geographical areas having physical features, such as tunnels, that may cause a loss of communication among locomotives in the train consist. When traveling through such areas the likelihood of RF communication loss among the lead and remote locomotives increases. Appropriately configured wayside RF repeaters may be placed near geographical areas that are known to cause communication difficulties in order to improve intra-train communication when a train consist passes through those areas. This increases the likelihood that a lead locomotive will receive reply messages from remote locomotives. Such wayside RF repeaters are relatively expensive to install and maintain and may be cost prohibitive to use in geographical areas that are difficult to access or that otherwise lack the necessary infrastructure to support their operation. Such wayside RF repeaters are also limited to operating only in their permanent physical geographic location. Train consists operating in areas lacking wayside RF repeaters are typically limited in their length to better ensure RF communication among the locomotives in the consist. Limiting the length of a train consist is disadvantageous to railroads that may otherwise maximize the length of a consist to meet customer demands, improve operating efficiency and maximize revenues.
In view of the above, it would advantageous to provide a reliable, cost effective method and system for improving the integrity of a distributed power communication system for verifying to the operator of a lead locomotive that all remote locomotives are following a set of command instructions.
Exemplary embodiments of the present invention fulfill the foregoing needs by providing in one aspect thereof a railroad distributed power communication method for wireless transceiver units at spaced locations along a train, with the train having a lead transceiver unit transmitting commands, remote transceiver units spaced from the lead and for which direct communication with the lead unit may be uncertain. The at least one intermediate transceiver unit may be located between the lead unit and at least one remote unit where the intermediate unit constitutes a repeater for repeating messages between the lead unit and at least one of the remote units. The method allows for verifying that a remote unit under the control of the lead unit is following a set of command functions broadcast by the lead unit in a command message by determining whether the lead unit has received a status reply message from the remote unit where the status reply message is transmitted in response to the remote unit""s receipt of the command message. The status reply message may include data indicative of at least one operational state of the remote unit. A help command message may be transmitted from the lead unit to the repeater in the event the lead unit has not received the status reply message from the remote unit. The help command message may be repeated from the repeater to the remote unit. A help reply message may be transmitted from the remote unit to the repeater in response to the remote unit""s receipt of the repeated help command message. The help reply message may be repeated from the repeater to the lead unit, the help reply message including data indicative of at least one operational state of the remote unit and the help reply message may be received at the lead unit thereby verifying that the remote unit is following the set of command functions.
In one aspect a method for communicating and verifying commands among a plurality of locomotives within a train consist is provided that comprises broadcasting a command message from a lead locomotive to at least one remote locomotive then determining whether the lead locomotive receives a status reply message including data indicative of at least one operational state of the remote locomotive. If the lead locomotive does not receive the reply message within a predetermined period of time after transmitting the command message then the lead may transmit a help command message. A help reply message may be transmitted from the remote locomotive in response to receipt of the help command message. The help reply message may be repeated from a remote locomotive consist and received by the lead locomotive. The help reply message may include data indicative of the at least one operational state of the first remote locomotive consist.
In another aspect a method for communicating among a plurality of mobile assets and verifying receipt of a message by at least one of the mobile assets is provided which comprises broadcasting a command message to the plurality of mobile assets then determining whether a lead mobile asset receives a status reply message from each of a predetermined group of the plurality of mobile assets. A help command message may be broadcast if the lead mobile asset did not receive a reply message from at least one of the predetermined group. The help command message may be repeated by at least one of the plurality of mobile assets and include data indicative of the identity of the mobile asset for which the lead mobile asset did not receive the reply message. A help reply message may be transmitted from the mobile asset for which the lead mobile asset did not receive the reply message, the help reply message being transmitted in response to receipt of the help command message. The help reply message may be repeated by at least one of the plurality of mobile assets and received by the lead mobile asset.
In another aspect a system for a lead locomotive to verify that a remote locomotive under the control of the lead locomotive is following a set of command functions broadcast by the lead locomotive in a command message, the lead and remote locomotives being part of a train consist equipped with a distributed power communication system is provided, which comprises a control module for determining whether the lead locomotive has received a status reply message from the remote locomotive where the status reply message is transmitted in response to the remote locomotive""s receipt of the command message and includes data indicative of at least one operational state of the remote locomotive. A transmitter for transmitting a help command message from the lead locomotive to a locomotive consist within the train consist in the event the lead locomotive has not received the status reply message from the remote locomotive. A radio unit for repeating the help command message from the locomotive consist to the remote locomotive and a transmitter for transmitting a help reply message from the remote locomotive to the locomotive consist in response to the remote locomotive""s receipt of the repeated help command message. A radio unit for repeating the help reply message from the locomotive consist to the lead locomotive, the help reply message including data indicative of at least one operational state of the remote locomotive and a receiver for receiving the help reply message at the lead locomotive thereby verifying that the remote locomotive is following the set of command functions.
The exemplary embodiments allow for cost effective and reliable communication among a plurality of mobile assets, such as locomotives within a train consist, for example. Train consists employing exemplary embodiments may increase their length, for example, and retain the ability to verify that all locomotives under the control of the lead locomotive are following instructions included in a command message. A repeating function of the exemplary embodiments is available one hundred percent of the time that is reliable, conserves communication resources and optimizes use of available on-board equipment.